johnson



May 20, 1941- M. J. JOHNSON LIGHT VALVE CONTROL 2 Sheets-Sheet l AAAAAA Original Filed April 5, 1936 .INVENTOR Mag red J Johnson Knows? May 20, 1941- M. J. JOHNSON LIGHT VALVE CONTROL Original Filed April 3, 1936 2 Sheets-Sheet 2 v INVENTOR 444W d J Joknso g i l ATTORNEYS Reissued May 20, 1941 UNITED STATES PATENT mice Mann-ed J. Johnson. Naug'atuck. Conn; or one-half to The Lewis Engineering Company,

Naugatuck, Conn.

Original No. 2,151,174, March 21, 193', 8c-

rial No.'i2,870, April 3, 1936. Application lot reissue January 20, 1940, SeriaiNo. 815,843

This invention relates to controls for potentiometer systems and the like, and more particularly to a continuously balancing controlled potentiometer for indicating and recording unknown quantities such as temperatures, and for controlling the operation oi apparatus so as to in my plioi patent, it had the disadvantage of using periodic contacts which resulted in a more or less step by step adjustment, of the slide maintain predetermined conditions, as in a iurnace.

An object of this invention is to provide an improved control tor recording potentiometers and the like which is particularly quick-acting and accurate, and which can be made very small and compact with economy of manufacture.

In carrying out the above object the present invention provides, with a potentiometer circuit, a continuously balancing control apparatus utilizing solely one photo sensitive cell and a lightv beam, the latter being shiited bya small mirror carried by a galvanometer.

It is disclosed in my Patent No. 1,910,340 to adjust the slide wire oi. a potentiometer system by an ordinary reversible electric motor under the control oi the directional movements of a galvanometer through periodic contacts actuated by the galvanometer.

In this prior proposal, the current was sent to the motor through the galvanometer needle and cooperating contacts, and this resulted in considerable arcing between the contacts. Also, the motor was not in all cases instantaneous in its action, as to starting and stopping. These diiliculties were to a large measure obviated by my more recent invention disclosed in Patent No. 1,971,313. In the latter, the directional contacts which cooperate with the galvanometer needle-contact controlled the grid circuits of thermionic devices or vacuum tubes, and in doing so caused the plate currents to operate a reversing clutch in one direction or the other according to which directional contact was engaged. i a

In my application Serial No. 35,151, filed August l, 1935, I have disclosed the use 01! a reversible shaded-pole A. C. induction motor for adjusting the slide wire, pointer, ruling pen, or other device oi the potentiometer circuit, while, at the same time employing thermionic devices to control the motor.

In this prior application, the galvanometer needle makes contact periodically with either of two metal strips carried by a drum which re. tates, so as to control the grids oi. the thermionic devices, which latter in 'turncontrol the rotation oi. the motor. While this arrangement was a considerable improvement over the disclosures wire and other devices.

Heretoiore, it was proposed to provide a plurality 01 light sourcesand one or more photoelectric cells for controlling the slide wire according to'the direction of oil-zero movement of the deflectable instrument depending upon the phase relation of the circuit at the time of ofl-zero movement.

In such devices, the photoelectric cell or cells controls the action of gaseous discharge tubes of the Thyratron type, with the result that the operation of the motor for adjusting the slide wire could not begin until the oil-zero movement of the deflectable instrument caused sufllcient light to impinge upon the photoelectric cell or cells to trip of! the gaseous discharge tube, and hence the slide wire motor only operated at maximum energization.

With such devices, continuous balancing control could not be obtained but only such step-byonic device proportionally to the amount oi light which impinges upon it. This amount of light depends upon the extent oi ofl-zero movement of the deflectable instrument, and hence the power applied to the motor operating the slide wire is in proportion to the extent of oiI-zero movement. o

It will be seen, therefore, that initial movement oi. the deflectablemember fronizero position will cause the light beam to move across the cell and illuminate a portion thereof, This will immediately affect the output of the thermionic device so that the motor operated thereby will move to restore the condition during the partial illumination of the cell in accordance with the amount oi light impinging thereon.

Thus, iilthe change in the condition is small,

it will causebut a slight oil-zero movement of the deflectable instrument, and hence the light beam, to partially illuminate the cell and cause the motor to start to turn slowly or creep and in the prior constructions. With these small variationsjthe motor will operate at a speed proportional to the amount of theillumination, and, in most cases, this slight movement will be sufficient to restore the balance and maintain the control substantially uniform.

However, if the change in the condition is large, the deflectable instrument will quickly shift the light beam to fully illuminate the cell and the thermionic device will apply its full power to the motor to cause it to operate at a maximum speed to again quickly restore balance. As a balanced condition is approached, the deflectable member will be shifted so as to decrease the illumination of the cell and the speed of the motor will then gradually decrease. Thus, as the zero point is approached, the motor is gradually moving slower and slower until it stops at the zero point, thereby preventing overshooting or hunting.

I have found that it is possible, as shown in one embodiment of the present invention, to control the grids of the thermionic devices according to the directional movements of the galvanometer by using only one light sensitive cell and a beam of light, which latter is directed by the movements of the galvanometer, and by periodically interrupting said beam of light by a shutter device synchronized with the impulses which energize the thermionic devices. By this means there has been obviated the step by step adjustment of the reversible'shaded-pole motor due to the periodic galvanometer contacts. and provided instead a continuously balancing control which enables a much quicker and more accurate adjustment of the potentiometer circuit, and of the devices to be controlled thereby.

In carrying out my invention, as embodied in a potentiometer circuit, I connect the wire-wound shading coils of the shaded-pole motor which controls the slide wire and other devices, through suitable transformer coupling, to the plates of the thermionic devices, and connect the grids of these latter in circuit with a light sensitive cell and a suitable source of direct current energy, and provide a light beam interrupting device so that impulses of the cell due to properly controlled light striking thereon will cause to function either of said thermionic devices, which ever is in condition, as determined by its plate energization, to function at that time.

The thermionic devices are so connected with the photo electric cell that impulses from the latter can affect equally the charge on both the grids of said devices, and the plates of these devices are energized through transformer coupling from the shading coils of the A. C. motor in such manner that at any instant, except for zero polarity, said plates will be oppositely charged, or will be in phase opposition. It will be noted that only when the plate of a thermionic device has a positive charge, is that de-' vice in condition to function, and therefore, according to the above'circuit, in order to have only one particular thermionic device function for a given period of time, proper charges are impressed on the grids of the devices only during the intervals when the plate of the particular device chosen to function is positive.

For light energization of the photo electric cell a continuous source of light is employed, this being reflected by a mirror attached to the galvanometer coil, and onto the photo sensitive cell.

For the purposes of the present invention, I provide a synchronous shutter interposed between the source of light and the light sensitive cell, and this shutter is adapted to cut oil! the light from the photo cell at predetermined periodic intervals during deflection of the galvanometer and mirror. and is adapted to shut off the light completely for zero or no-deiiectlon position of the galvanometer.

The light which reaches the photo electric cell is therefore interrupted by means of the shutter and according to the direction of the deflection of the galvanometer so as to cause periodic charges to be impressed on the grids of the thermionic devices, such that that device will function which causes movement of the motor controlling the slide wire in a direction to balance the po-- tentiometer circuit, and to thereby cause consequent return of the galvanometer to zero position,

In accomplishing this control, as embodied in the potentiometer system, the shutter is syn-. chronized with the alternating current energization of the thermionic devices in such a manner that for a given direction of deflection=of the galvanometer, light will be permitted to strike the photo sensitive cell only during the periods when one particular thermionic device has its plate positively charged and is therefore in condition to function. This device, in functioning, causes a loading of one set of shading coils of .the motor, and this loading results in rotation of said motor in one direction. When the galvanometer deflects in the opposite direction, the light striking the photo cell will be so timed, by means of the synchronized shutter, as to cause to function the other thermionic device, resulting in a loading of the other pair of shading coils of the motor. and consequent movement of the latter in the opposite direction.

It should be noted that the interruptions in the light beam by the synchronous shutter are of such rapid frequency that there will be effected a continuous movement of the adjusting motor when either of the thermionic devices is functioning to cause rotation thereof.

When the potentiometer circuit is in a balanced condition there will be obviously no deflection of the galvanometer, and the beam of light which is reflected from the mirror carried thereby will be at all times prevented from striking the photo sensitive cell by a light obstructing portion of the synchronous shutter, and therefore since no impulses will be impressed on the grids of the thermionic devices these will not function, and

the motor and attached slide wire will remain at rest.

It is thus seen that the present invention provides by means of solely one photo sensitive cell and a synchronized shutter interrupting a light beam, a continuously balancing exceptionally quick-acting and sensitive control for potentiometer circuits or other systems, and a control which slot is of a length to extend an angular distance of 90, 'and the disk is rotated at a synchronous speedby means of a synchronous motor.

a steel reed having a light obstructing portion moving before windows in a metal plate, the reed vibrating in front of a soft-iron pole-piece at-' tached to a permanent magnet, and according to the impulses of an AL 0. coil carried by said pole piece.

The present invention is also not to be limited to the particular type of shutter disclosed, and any other suitable type of synchronised shutter may be used between the photo sensitive cell and the source of light for said cell.

Also, no limitations are intended to be indicated by the particular type of photo sensitive cell shown, and the herein disclosed embodiments are merely for illustrative purposes.

Other features and advantages will hereinafter appear.

In the accompanying drawings:

Figure 1 shows one embodiment of the present invention, and pictures a source of light, galvanometer, synchronous shutter disk, and photo sensitive cell in their approximate physical relationship, and also a diagrammatic representation of the circuits and apparatus associated therewith.

Fig. 2 is a plan view of the disk used in the synchronous shutter shown in Fig. i.

Fig. 3 shows the connections for a conductive type of photo electric cell.

Fig. 4 is a perspective view of a vibrating reed type of synchronous shutter and the approximate physical relation of this with a source of light, a galvanometer and a photo sensitive cell.

Referring now the the system diagrammatically illustrated in Fig. 1, the potentiometer circuit which is used with the thermocouple or other source of voltage varied according to a change of conditions includes a primary source of energy in the form of a battery III which is connected by means of a wire ii to a variable calibrating wireILandbymeansofawhelltoanalternative contact of the switch II.

' 35,151, filed August "1, 1935, the use of a reversible shaded-pole alternating current motor conresistance i2, and by means of a wire II to one end of a slide wire mounted on the periphery of a stationary disk ii. The other end of the slide wire I4 is connected by awire It to a resistor il which in turn is connected by a wire l8 to the other end of the calibrating resistance II. A

resistor I9 is shunted across the slide wire it for the purpose of reducing the voltage drop across the latter. A complete circuit is thus formed through the slide wire l4 and shunted resistance [9, the resistor H, the calibrating re- 1 sistance i2, and the battery "I and current flows through this circuit as a result.

A galvanometer 20 is attached by means of a wire II to one end of the slide wire II, and by means of a wire 22 through a switch 23 to. a thermocouple II which in turn is connected by a wire 25 to a slider It which moves around the disk I! and contacts with the slide wire l4. Thus the galvanorneter 20 and the thermocouple 24 are shunted across a portion of the slide wire I, as determined by the position of the slider 28, and it is possible, by adjustment of said slider and the calibrating resistance I2, to secure a balanced condition such that no deflection of the galvanometer results. For the purpose of checking the potential drop across the slide wire it of the potentiometer circuit just described, a standard cell 21 is connected by means of a wire 28 to the trolled by thermionic devices, which in turn were under the control of movements of the galvanometer, the motor being employed to move the slider of the potentiometer system.

The system diagrammatically illustrated in Fig. 1 employs a similar induction motor 82 under the control of similar thermionic devices, said motor having a squirrel cage rotor 33 and a continuously energized A. C. field 34. The motor 32 has a pair of oppositely disposed shading coils 35 connected in series and a second pair of oppositely disposed shading coils 38 also connected in series. The shading cells 35 and 35 are so disposed on the pole pieces of the motor that loading of one set of shading coils will cause rotation of the motor in one direction, and loading of the other set of shading coils will cause rotation of the motor in the other direction.

One end of the series-connected coils II is joined by means of a wire 81 to one end of the series-connected coils l6, and this juncture is connected by means of a wire 18 to the center tap 39 of the primary winding ill of a transformer ll. One end of the primary winding ll is connected by a wire I! to the remaining end of the seriesconnected shading coils I6 and the other end of the primary winding 40 is connected by means of a wire 43 to the remaining end of the series-connected shading coils 35.

The transformer H is used to couple the plates of thermionic devices to the shading coils, as hereinafter disclosed. By virtue of the constant A. C. energization of the field 3| of the motor there will be voltages induced in the shading coils 35 and 36 thereof and these voltages will be impressed on the primary 40 of the transformer ll and will result in a continuous energization of said transformer, which energization is of the same frequency as that of the field 3|, and has a definite phase relationship thereto.

The field 34 of the motor is connected by wires 44 and 45 to main A. C. supply wires 48 and H, and therefore the energization of the transformer 4i has a definite phase relationship with the energy carried by these supp y wires.

The transformer II has a secondary coil 48 having one end connected by a wire I! to the plate or anode of a thermionic device 50, and having the other end connected by a wire ii to the plate of a thermionic device 52. The thermionic devices 50 and 52 are of the three-electiiooie type, each having a filament, a grid, and a p a e.

There is thus impressed on the plates of the thermionic devices 50 and 52 an alternating voltage from the transformer Ii and at any instant the polarity of one plate will be opposite to the polarity of the other plate and the charges thereon will alternate in phase with the energy of the supply wires 46 and 41. The filaments of the thermionic devices It and 52 are connected in parallel by wires 53 and I4, and these latter are respectively connected by wires I! and II to the secondary ll of a filament supply transformer II, the primary I! of which is connected by wires I! and ll to the supply wires II and 41 respectively.

The secondary 4| of the transformer ll has a center tap 82 which is connected by a wire 83 to the wire ll which leads from the filament transformer, and therefore the charges impressed on the plates of the thermionic devices ill and I! are measured substantially with reference to the filaments of these devices.

The grids of the thermionic devices 50 and I! are connected together by a wire 64, and this wire is connected, through a wire it and a suitable grid resistor 05 and a wire I1, to the point A, representing the negative side of a suitable source of direct current energy supply to be hereinafter described. The positive side of this source of D. C. energy, point B, is connected by a wire timed intervals a suitable positive charge on the grids of the thermionic devices ill and 52, that device which has its plate positive during said intervals will be made to function, and will, through the transformer coupling means 4 l load its associated shading coils of the motor and cause rotation thereof.

Functioning of the thermionic device 50 will cause rotation of the motor in one direction, and functioning of the thermionic device 52 will cause rotation of the motor in the opposite direction.

The present invention is primarily concerned with the method of, and means for, controlling rotation of the motor directionally in accordance with the direction of deflection of a deflectable member. In the present embodiment, this includes causing to function the thermionic devices It and 52, using solely one photo sensitive cell by impressing charges on the grids of said devices in accordance with the off-zero movements of the galvanometer 20 and such that deflection of the galvanometer in one direction will cause to function one of said thermionic devices, and deflection of the galvanometer in the other direction will cause to function the other of said thermionic devices.

For this purpose there is provided a unique form of control including a beam of light reflected by a mirror attached to the galvanometer, and reflected through a synchronous shutter onto a photo sensitive cell which is in circuit with the grids of the thermionic devices.

In the embodiment of Fig. 1, there is provided a source of light 68 which is preferably in the form of an incandescent bulb connected by wires ll and II through the wires H and 4! to the supply wires 46 and IT. The source of light 69 has a reflector 12 associated therewith for directing a beam of light against the mirror II attached to, the coil of the galvanometer ",and the light 69 and mirror I8 are so disposed that the beam of light is reflected toward a photo sensitive cell ll, of the emissive type.

The photo sensitive cell 14 has one terminal connected by a wire I! to the wire 68 which joins cases to the common filament connection of the thermionicdeviceaandhsstheothertermimiconnectedbyawirelitoaresistor'llanmthrough awire'lttoagridcondenserll'. Thecondenser II has its remaining terminal connected by a wire'lltothewirellwhichisioinedwiththe gridresistor",aridtheremainingt'ei'lnilialof the resistor ll is connected across thefwires I and BI of the direct current supply.

By so connecting the photo sensitive cell ll inthegridcircuitsofthethermionicdevicesll andll,light,instrikingsaidceil,willcausea charge therefrom which will have the eifect'of reducing the negative polarity of the grids and in some cases even resulting in grids of zero or slightly positive polarity. From the academic standpoint, a steady light, in striking the photo sensitive cell ll will so affect the grids that the thermionic devices 50 and 52 will function whenever their plates are positively charged, and since these latter are in phase opposition, one device will start to function as soon as the other device has stopped functioning and so on, the devices alternately functioning in step with the alternations of the plate charges.

However, for the practical purposes of its obiectives, the present invention provides for intermittently breaking or cutting the beam of light from the galvanometer 20 to the photo sensitive cell It by means of a synchronized shutter in such a manner that light will strike said cell at properly timed intervals so as to cause to function only one of the thermionic devices, the particular device chosen being according to the direction of deflection oi thegalvanometer, and for zero deflection of the galvanometer the light will be completely shut off from the cell. Thus if the galvanometer is deflected to the left, light will strike the photo sensitive cell only at those times during which a positively charged plate exists in that thermionic device which when functioning loads the shading coils of the motor so as to move the slider 28 in the direction required to lessen the left deflection of the galvanometer. It follows also that a right deflection of the galvanometer would, as a consequence, make the photo sensitive cell cause to function the other thermionic device, which causes the motor to rotate the slider 2liso as to lessen the right deflection of the galvanometer. Thus there is affected a balancing of the potentiometer circuit, and it is to be noted that the frequency or interruption of the light beam is sufliciently high so that the movement of the motor, in balancing the circuit is not a step by step movement, but is of a substantially continuous nature.

The embodiment of the present invention shown in Fig. 1 provides for intermittently interrupting the light beam by using a synchronized shutter including a disk 88, which isrotated at a synchronous speed having a constant phase relationship with the energization of the motor 32 by means of a synchronous motor 84 connected by wires 85 and 88 to the wires 44 and 45 which receive energy from the common A. C. supply wires 48 and ii. The disk 83, see Fig. 2, has two pairs of arcuate-shaped slots 81 and 88 disposed therein about the periphery thereof, the slots of each pair being oppositely disposed of the center 89 of the disk, and each pair being angularly displaced 90 from the other. Each slot of a pair has a length such that it extends through an angular displacement of 90, or the equivalent of a quadrant of a circle.

a1,soe I the mirror attached thereto will be prevented I of one pair are disposed closer center 88 than are theslots of the other radial distance substantially equal to twice the width of aslot. V

Whenthediskisrotatinmthereistlursprm vided between the annular areas covered by the outer slots 81 and the inner slots 88 a solid portion which forms a barrier for light reflected from the mirror of the galvanometer, the width of said barrier. portion being substantially, therefore, equal to the width of a slot.

As the beam is deflected either to the right or left, initial movement of the beam will cause it to pass from the barrier and into the slot to illuminate a portion of the cell. Continued increase in deflection will illuminate the whole area of the slot. When this condition is reached, further changes in condition, which would normally increase the deflection, will operate to hold the deflectable member in a position wherein the entire slot is illuminated.

from reach-lug the photo sensitive cell II because of the obstruction oii'ered to it by the solid barrier portions of the disk 88 intermediate the areas covered by the both pairs of slots therein..

The'balancing operations as directed by the deflection of the galvanometer and using solely the one photo sensitive cell will be quickly responsive to the unbalance of the potentiometer circuit, and by virtue of this and thecontinuously acting nature of the control movement as out- In order to maintain thegrids of the therme ionic devices normallynegative, there is shown tive'side' connected at A to the wire 81, and its.

When using thermionic devices as described,

immediately, upon thebeam being shifted to the right or left, to illuminate a small portion of the cell, a pulsating current, proportional to the amount of illumination of the cell, will be setup and the grids will have a potential applied thereto which will cause the proper thermionic device to apply an output, proportional to the illumination of the cell, to the motor so that the motor operates in accordance wtih theextent of illumination of the cell,

It is to be understood that the amount of deflection necessary to cause the beam to travel to a position in which it fully illuminates the slot is but a very small proportion of the range of the instrument. Thus it will beseen that for very small changes in the condition, thespeed oi the balancing motor will be in proportion to the change. y r

However, for large changes in condition, the slot will very quickly be fully illuminated and the motor will run at full speed until rebalance is approached and the reflecting means will move the beam of light back across the slot. when this occurs, it will be apparent that the speed oi the motor will be decreased from its full speed during the last small fraction of unbalance and the decrease will be such that, upon balance being reached in the circuit, the motor will be operating at such a low speed that it will stop immedlat'ely upon the beam moving to the barrier and thus prevent overrunning and hunting.

The disk 88 is so adjusted upon the shaft of the motor 84 that the outer pair of slots 81 will permit light from the galvanometer, when deflected to the left, to strike the photo sensitive cell 14 only during those periods when the plate of one of the thermionic devices is positive and therefore when that device is in condition to in Fig. 1 a rectifler and fllter receiving energy from the main supply wires and having its negapositive side connected at B'to the wire 88. This direct current supply for the grid circuit includes a transformer 88 having ,a primary winding 8I- The filaments of the tubes 81 and 88 are confunction so as to cause rotation of themotor 82,

and that thermionic device is chosen which will cause the slider 28 to move in a direction which will reduce the left deflection oi the galvanometer. I Therefore, the inner pair of slots 88 of the disk 88 will permit light from the galvanometer mirror, when deflected to the right, to strike the photo sensitive cell only during those periods when the other of said thermionic de-- vices is in a position to function by virtue of its plate being positive, and to cause a movement nected in parallel by wires 88 and I88, which are joined respectively by wires IM and I82 to a filament winding I88 of the transformer 88.

The remaining terminal of the condenser I8! is connected by a wire II8 to the wire I88, and this latter is also connected by a wire III to a second filter condenser'i I2 which has its remaining terminal connected through a wire M8 to the choke coil I85. A wire Ill connects the choke coil I85 with the wire 81 of the grid circuit. There is thus provided a means for maintaining the grids of the thermionic devices 58 and at a negative potential with respect to the filaments thereof, so that said devices are normallyinoperative due to limited or no-plate current. it should be understood that any other suitable supply of direct current energy, such as a battery, may be connected between the points A and B in place of the rectifier and fllter just described. I Another embodiment of the present invention, as shown in Fig. 3 discloses the use of a conducting type of photo sensitive cell, in place of the emissive type shown in Fig. 1. It is desired, however, that the present invention be not limited to the specific type of light sensitive cell or I4 and its associated circuit oi Fig. 1 included of the slider 28 such that the right deflection of the galvanometer will be lessened. Of course, for a balanced condition of the potentiometer circuit and zero position of the galvanometer, light from between the letters A, B, C and D.

One terminal of the cell H5 is connected by a wire 8 to the point B for connection with the positive side of the grid energy supply, and the other terminal is connected by' a wire I H to a wire 8 leading to C, for connection to the grids of the thermionic devices. The wire Ill connects with a grid resistor N8, the other terminal of which is connected by a wire I28 to the point A.

Two resistors I2I and I22 have a common connection I28 which is joined by a wire I24 to the point D, and the remaining ends of these resistors are respectively connected to the wires I28 the conductive type of photo sensitive cell III is similar to the action with the emissive type of cell 14 as described;

In Fig. 4 is shown another form of synchronous shutter for use in the light beam control of the present invention. This shutter is interposed between the light-sensitive cell Ida. and the mirror no of the galvanometer 200., which mirror has light directed at it by the reflector 12a of the light source "a. The synchronous shutter includes a permanent magnet I25 having one pole shorter than the other and having a soft-iron pole extension I28 attached to the shorter pole, with an alternating current coil I21 wound thereon for energization by wires I28 and II! from the A. C source of supply associated with the reversible slide wire motor of the system.

A thin steel reed I" is supported vertically at the longer pole of the permanent magnet in such a manner that it may vibrate freely back and forth before the end the soft-iron pole piece III carrying the coil I21. Attached to the steel reed III is an aluminum vane III which moves back and forth across openings I32 and I in a flat shutter'piece I vertically supported behind the vaneby brackets ill. Between the openings I32 and Ill there is provided a light-obstructing portion Ill, and it is preferable to have said apertures and said light-obstructing portion of one width, which width is the same as that of the aluminumvane Ill.

By having the energizing coil I21 wound on the soft-iron core extension oi a permanent magnet III, the reed III will be caused to vibrate in-synchronism with the alternating current or the coil,

III will be synchronized with the alternating charges on the plates of said devices, and deflection of the galvanometer in one direction or the other will result in one or the other 01' said thermionic devices functioning to cause proper rotation to the shaded-pole motor for establishing a balance .of the potentiometer circuit.

In the broader aspects of this invention any suitable form of synchronous shutter other than the particular types disclosed herein may be used.

As in my application above referred to; the pointer III which turns with the slider 26 on the slide wire l4 may be used to indicate directly temperatures of the ;thermocouple 24, and a visible and permanent recording may be had by using a pencil-cooperating with a timed control graph sheet. The movement 01 the sliding contact I6 and shaft ll may also be used to open means for operating said means for causing movement 01' the eleetro-respon'sive device; and means for controlling a beam of light to intermittently strike said light responsive means actively responding to the periodic impulses oi thelight-sensitive means so as to cause movement of the electro-responsive means in one direction or the other, the direction of movement depending on whichever particular set of periodic impulses is being set up by the light responsive means in responding to the deflectable member.

3. In a system for electing a control in response to a change in magnitude of a condition, the method which comprises producing a single beam or light; deflecting said beam in accordance with the change in magnitude of a condition;

producing pulsations in said deflected beam in predetermined phase relationship according to the direction oi. deflection; impressing the pulsating beam on a light sensitive means; operat- 4 ing thermionic devices in accordance with the ance with the change in magnitude of a condie tion; producing pulsations in said deflected beam in predetermined phase relationship according to the direction of deflection; impressing the pulsating beam on a light sensitive cell to produce a constant frequency electric current dependent in phase position upon the direction of change in the magnitude of said condition; di-

. recti'ng said current to a plurality of controlling or close switches at predetermined times for actuating apparatus for control purposes.

Variations and modifications may be made.

means, each responding to a different predetermined phase position of the current; and operating' an electroresponsive control by said controlling means.

5. In a system for effecting a control in response to a change in magnitude of a condition, the method which comprises producing a single beam of light; deflecting said beam in accordance with the change in magnitude of a condition; producing pulsations in-said deflected beam in predetermined phase relationship according to the direction of deflection; producing an electric current to produce fluctuations oi the current I according to a constant "frequency and so that the phase position of said current is representative of the direction or change in magnitude of 2. In combination, light-sensitive current pro- I and means connected with -'the said condition; and selectively directing said current through control circuits.

' 6. In a system for effecting a control in response to change in magnitude of a condition,

the method which comprises producing asingle periodically interrupted beam of radiant energy having a constant period, and whose phase position is dependent upon the sense of change in the magnitude of said condition, eifecting variations in an electric current corresponding in time with theperiod of said beam, and selectively directing said current through on of a plurality of circuits for effecting a control.

'7. In a system for effecting a control in response to a change in magnitude of a condition, the method which comprises producing a single beam of light; deflecting said beam in accordance with the change in magnitude of a condition; producing pulsations in said deflected beam in predetermined phase relationship according to the direction of deflection; varying a resistance in an electric circuit carrying a current of constant magnitude to produce a constant frequency electric current dependent in phase position upon the phase relationship of said pulsating beam;

and selectively directing said current through one of a plurality of circuitsfor eiiecting a control.

8. In a system for effecting a control in response to change in magnitude of a condition, the method which comprises producing an electriccurrent of constant frequency and magnitude, interrupting a single beam of light to produce a phase displacement of said current substantially 90 in response to change in the magnitude of said condition, and selectively directing said current according to its phase position through one of a plurality of circuits for efl'ecting a. control.

9. A control apparatus comprising a source of light; a light-sensitive cell; deflecting means responsive to change in magnitude of a condition for directing a beam of light from said source upon the light-sensitive cell; means for producing constant frequency pulsations in said beam having a phase position dependent upon the direction of deflection of said deflecting means with respect to a neutral position; and electrical control circuits connected to said light-sensitive cell.

10. A control apparatus comprising a deflecting member; reflecting means associated with said member for directing a beam of radiant energy upon a variable resistance cell included in an electric circuit; and means for producing constant frequency pulsations in said beam having a phase position dependent upon the direction of deflection of said member whereby there is produced a fluctuating current in said circuit which is phase displaced according to the direction of deflection of the deflecting member.

11. A system for eiIecting a control in response to change in magnitude of a variable, comprising current-producing means and a circuit therefor;

a light-responsive c ll in said circuit; means responsive to change in the magnitude of said condition for directing a beam of radiant energy upon said cell; means for producing constant frequency pulsations in said beam having a phase position dependent upon the sense 01' change in the magnitude of said condition whereby there is produced a fluctuating current in said circuit which is phase displaced according to the sense of change in the condition; means for causing said current to selectively flow, according ,to its phase position, through one of a plurality of circuits; and electro-responslve means selectively traversed by the current, for effecting a control.

12. A system for eifecting a control in response to change in magnitude of a variable, comprising current-producing means and a. circuit therefor; a light-responsive cell in said circuit; means for producing a beam of radiant energy to actuate said cell; means, including a shutter for periodically interrupting the beam, and a beam-directing device responsive to changes in the magnitude of said condition, for. producing constant frequency pulsations in the, beam having a phase position dependent upon the sense of change in the magnitude of said condition whereby there is produced a fluctuating current in said circuit which is phase displaced according to the sense of change in the condition; means for causing said current to selectively flow, according to its phase position, through one of a plurality of circuits; and electro-responsive means selectively traversed by the current, for effecting a control.

13. A system for effecting a control in response to change in magnitude of a condition, comprising means for producing an electric current; means for producing constant frequency fluctuations in said current and for phase displacing said current to a substantially quadrature position in response to change in the magnitude of said condition, including a single light source producing a single light beam and means to periodically interrupt said beam; 9. pair of electron-emission devices connected to said currentproducing means; means for energizing said devices in phase opposition to caus them to selectively respond to the phase positions of the fluctuating current; and electro-responslve means connected with said devices and controlled according to the selective responses thereof.

.14. In a potentiometer system, an adjustable slide wire and circuit therefor; means for adlusting the slide wire, including an electro-responsive device operative in reverse directions; control circuits connected with said device; a light-sensitive cell connected to said control .circuits; a source of light; means for directing a beam of light from said source upon thelightsensitive cell; means for deflecting said directing means in either of opposite directions from a neutral position in response 'to energy change in the slide wire circuit; means for producing constant frequency pulsations in said beam having a phase position dependent upon the direction of deflection of said light-directing means with respect to the neutral position so that a pulsating current flows in the control circuits with a phase position corresponding to that of the pulsations in the light beam; andmeans for selectively operating the electro-responsive device directionally according to the phase position of the pulsating current in said control circuits to adjust the slide wire.

15. In a potentiometer system, an adjustable slide wire and circuit therefor; means for adjusting the slide wire, including an electro-responsive device operative in reverse directions; control circuits connected with said device; a light-sensitive cell connected to said control circuits; a source of light; means for directing a beam of light from said source upon the light-sensitive cell; means for deflecting said directing means in either of opposite directions from a neutral position in response to energy change in the slide wire circuit; means for producing constant frequency pulsations in said beam having a phase position dependent upon the direction of deflection of said light-directing means with respect to a neutral position so that a pulsating current flows in the control circuits with a phase position corresponding to that of the pulsations in the light beam, the frequency of said pulsations being relatively rapid with respect to the deflecting movement oi. said directing means so that at least several pul sations occur during any deflection; and means for selectively operating the electro-responsive device directionally according to the phase position oi the pulsating current in said control circircuits: a source light; means for directing.

a beam of light from said source upon the lightsensitive cell; a galvanometer' connected in the slide wire circuit and operating said directing means to deflect same in either of opposite directions from a neutral position in response to energy change in the slide wire circuit; means for producing constant frequency pulsations in said beam having a phase position dependent upon the direction of deflection of the galvanometer so that a pulsating current flows in the control circuits having a phase position corresponding to that of the pulsations in the light beam; and means for selectively controlling the shading coils to operate the electro-responsive device directionally according to the phase position 0! the pulsating current in said control circuits to ad- Just the slide wire.

cording to the direction of deflection of said beam; a circuit including a light sensitive means, said light sensitive means receiving the pulsating light beam and varying the current in said circuit in accordance with the illumination thereof; thermionic devices rendered operative in accordance with the variation of current in said circuit by said light sensitive means; and electro-responsive means controlled by said thermionicmeans for eflecting a control.

19. he system i'or effecting a control in response to a change in magnitude of a condition, asingle beam of light; means for deflecting said beam in accordance with the change in magnitude or a condition; means for producing pulsations in said deflected beam in predetermined phase relationship according to the direction of deflection of said beam; a pair of thermionic devices; means including light sensitiv means illuminated by the pulsating light beam for regulating the output of said devices in accordance with the extent of illumination of the light sensitive means and in accordance with the phase relationship of said deflected beam; and electroresponsive means operated by the output of said devices to effect a control.

20. A control system comprising a selectively controlled electro-responsive means; a pair oi thermionic devices connected with said means so that respective functioning of said devices will selectively control said means; means for energizing said device in phase opposition so that they are in condition to function alternately; a source of light producing a single beam; means for deflecting said beam; means for producing a control current; a circuit therefor including a light sensitive cell to be illuminated by said beam connected to said devices; means for in- I terrupting the beam to produce constant frequency fluctuations in said current synchronized with the energization of the thermionic devices so that only one device will operate in accordance with the illumination of the cell; and a means for shifting the phase relationship of said current relative to the energization of the thermionic devices so that the other device will operate.

MANFRED J. JOHNSON. 

